Summary
What may be viewed as a relatively simple system, the
beach, underlain mainly by sand, can in fact frequently
manifest a variable and spatially complex system. In an
estuary, the beach, as a shoreline deposit, spans the range
of environments from the river entrance to the marine
estuarine mouth. Estuarine beaches, whether as a long
continuous shoreline or as a discontinuous set of pocket
beaches, traverse three major environments in terms of
hydrodynamic setting, hydrochemistry, macroscopic biological setting, microscopic biological setting, and sediment provenance. As such, the beach in estuaries is
subject to five major environmental gradients (Figure 9).
In terms of hydrodynamic setting, there is the part of the
estuary located at/near the marine environment that is dominated by ocean waves and, to a lesser extent, by intraestuarine wind waves, tides, and onshore winds; there is
the central estuary dominated by intra-estuarine wind
waves, wind, and lesser effects from tides, river current,
and floods. There is the riverine part that is dominated by
river currents, wind waves, wind, and, to a lesser extent,
tides. In terms of hydrochemistry, there is the marine part
that is dominated by marine salinities and the attendant
effects on biota and their biological processes and marine
authigenesis/diagenesis. There is the central estuary dominated by fluctuating salinities or brackish waters, the attendant effects on biota and their biological processes, and
estuarine authigenesis/diagenesis. There is the riverine part
that is dominated by freshwater and its attendant biological
and authigenesis/diagenesis products. In terms of biological
setting, there is the marine part that is dominated by marine
assemblages. There is the central estuary dominated by
euryhaline biota specialized for estuarine conditions. There
is the riverine part that is dominated by freshwater biota. In
terms of sediment provenance, the tripartite subdivision of
estuaries is reflected in the exogenic sedimentary particles
(those derived outside of the estuarine basin) in that there
is a marine component dominantly towards the estuarine
mouth, a mixed component in the central estuary, and
a riverine component towards the river mouth. The tripartite
subdivision of estuaries also is reflected in the composition
of endogenic sedimentary particles and sediment types
(those derived inside the estuarine basin) in that peat and
bioclasts (shells) are diagnostic of freshwater parts of the
estuary (though peat is not within the beach environment;
its presence leeward of beaches adds hydrochemical complexity to freshwater seepages). As such, the beaches of
the estuary provide a framework to viewing and studying
beach processes across the longitudinal range of estuarine
environmental variability.
This variability of beach setting within the estuary and
the beach processes relative to beach setting is expressed
geomorphologically, stratigraphically, lithologically, biologically, and authigenically/diagenetically.
At smaller scales, the physical, biological, and chemical
processes operating on beaches result in environmentspecific features such as sedimentary structures, specific
suites of lithology such as laminated sand, or concentrations of shell and rock gravel, shell lenses, burrow
structures, bioturbation, and chemical products. These
environment-specific processes and products are preserved
geohistorically in the evolving stratigraphy under the estuarine beach (Figure 10).
Bibliography
Abril, G., Etcheber, H., Delille, B., Frankignoulle, M., and
Borges, A. V., 2003. Carbonate dissolution in the turbid and
eutrophic Loire estuary. Marine Ecology Progress Series, 259,
129–138.
Aller, R. C., 1988. Benthic fauna and biogeochemical processes in
marine sediment: the role of burrow structures. In Blackbum,
T. H., and Sorensen, J. (eds.), Nitrogen Cycling in Coastal
Marine Environments. New York: Wiley, pp. 301–338.
Aller, R. C., 2004. Conceptual models of early diagenetic processes:
the muddy seafloor as an unsteady, batch reactor. Journal of
Marine Research, 62(6), 815–835.
Alongi, D. M., 1985. Microbes, meiofauna, and bacterial productivity on tubes constructed by the polychaete Capitella capitata.
Marine Ecology Progress Series, 23, 207–208.
Arrieta, N., Goienaga, N., Martínez-Arkarazo, I., Murelaga, X.,
Baceta, J. I., Sarmiento, A., and Madariaga, J. M., 2011.
Beachrock formation in temperate coastlines: examples in
sand-gravel beaches adjacent to the Nerbioi-Ibaizabal Estuary
(Bilbao, Bay of Biscay, North of Spain). Spectrochimica Acta.
Part A, Molecular and Biomolecular Spectroscopy, 80(1),
55–65, doi:10.1016/j.saa.2011.01.031.
Barton, L. L., and Fauque, G. D., 2009. Biochemistry, physiology
and biotechnology of sulfate-reducing bacteria. Advances in
Applied Microbiology, 68, 41–98.
Bates, L., and Jackson, J. A. (eds.), 1987. Glossary of Geology.
Alexandria: American Geological Institute.
Bathurst, R. G. C., 1975. Carbonate Sediments and Their Diagenesis, 2nd edn. Amsterdam: Elsevier.
Behrens, E. W., and Watson, R. L., 1969. Differential sorting of
pelecypod valves in the swash zone. Journal of Sedimentary
Petrology, 39(1), 159–165.
Berner, R. A., 1981. Authigenic mineral formation resulting from
organic matter decomposition in modern sediments. Fortschritte
der Mineralogie, 59, 117–135.
Berner, R. A., and Raiswell, R., 1984. C/S method for
distinguishing freshwater from marine sedimentary rocks. Geology, 12, 365–368.
Bianchi, T. S., 2007. Biogeochemistry of Estuaries. Oxford: Oxford
University Press.
Boer, P. L. D., 1979. Convolutions lamination in modern sands of
the estuary of the Oosterschelde, The Netherlands, formed by
entrapped air. Sedimentology, 26, 283–294.
Boyle, E. A., Edmond, J. M., and Sholkovitz, E. R., 1977. The
mechanism of iron removal in estuaries. Geochimica et
Cosmochimica Acta, 41, 1313–1324.
Brocx, M., and Semeniuk, V., 2009. Coastal geoheritage:
encompassing physical, chemical, and biological processes,
shoreline landforms and other geological features in the coastal
zone. Journal of the Royal Society of Western Australia, 92,
243–260.
Brocx, M., and Semeniuk, V., 2011. The global geoheritage significance of the Kimberley Coast, Western Australia. Journal of the
Royal Society of Western Australia, 94, 57–88.
Brown, A. C., and McLachlan, A., 1990. Ecology of Sandy
Beaches. Amsterdam: Elsevier.
BEACH PROCESSES
71
What may be viewed as a relatively simple system, the
beach, underlain mainly by sand, can in fact frequently
manifest a variable and spatially complex system. In an
estuary, the beach, as a shoreline deposit, spans the range
of environments from the river entrance to the marine
estuarine mouth. Estuarine beaches, whether as a long
continuous shoreline or as a discontinuous set of pocket
beaches, traverse three major environments in terms of
hydrodynamic setting, hydrochemistry, macroscopic biological setting, microscopic biological setting, and sediment provenance. As such, the beach in estuaries is
subject to five major environmental gradients (Figure 9).
In terms of hydrodynamic setting, there is the part of the
estuary located at/near the marine environment that is dominated by ocean waves and, to a lesser extent, by intraestuarine wind waves, tides, and onshore winds; there is
the central estuary dominated by intra-estuarine wind
waves, wind, and lesser effects from tides, river current,
and floods. There is the riverine part that is dominated by
river currents, wind waves, wind, and, to a lesser extent,
tides. In terms of hydrochemistry, there is the marine part
that is dominated by marine salinities and the attendant
effects on biota and their biological processes and marine
authigenesis/diagenesis. There is the central estuary dominated by fluctuating salinities or brackish waters, the attendant effects on biota and their biological processes, and
estuarine authigenesis/diagenesis. There is the riverine part
that is dominated by freshwater and its attendant biological
and authigenesis/diagenesis products. In terms of biological
setting, there is the marine part that is dominated by marine
assemblages. There is the central estuary dominated by
euryhaline biota specialized for estuarine conditions. There
is the riverine part that is dominated by freshwater biota. In
terms of sediment provenance, the tripartite subdivision of
estuaries is reflected in the exogenic sedimentary particles
(those derived outside of the estuarine basin) in that there
is a marine component dominantly towards the estuarine
mouth, a mixed component in the central estuary, and
a riverine component towards the river mouth. The tripartite
subdivision of estuaries also is reflected in the composition
of endogenic sedimentary particles and sediment types
(those derived inside the estuarine basin) in that peat and
bioclasts (shells) are diagnostic of freshwater parts of the
estuary (though peat is not within the beach environment;
its presence leeward of beaches adds hydrochemical complexity to freshwater seepages). As such, the beaches of
the estuary provide a framework to viewing and studying
beach processes across the longitudinal range of estuarine
environmental variability.
This variability of beach setting within the estuary and
the beach processes relative to beach setting is expressed
geomorphologically, stratigraphically, lithologically, biologically, and authigenically/diagenetically.
At smaller scales, the physical, biological, and chemical
processes operating on beaches result in environmentspecific features such as sedimentary structures, specific
suites of lithology such as laminated sand, or concentrations of shell and rock gravel, shell lenses, burrow
structures, bioturbation, and chemical products. These
environment-specific processes and products are preserved
geohistorically in the evolving stratigraphy under the estuarine beach (Figure 10).
Bibliography
Abril, G., Etcheber, H., Delille, B., Frankignoulle, M., and
Borges, A. V., 2003. Carbonate dissolution in the turbid and
eutrophic Loire estuary. Marine Ecology Progress Series, 259,
129–138.
Aller, R. C., 1988. Benthic fauna and biogeochemical processes in
marine sediment: the role of burrow structures. In Blackbum,
T. H., and Sorensen, J. (eds.), Nitrogen Cycling in Coastal
Marine Environments. New York: Wiley, pp. 301–338.
Aller, R. C., 2004. Conceptual models of early diagenetic processes:
the muddy seafloor as an unsteady, batch reactor. Journal of
Marine Research, 62(6), 815–835.
Alongi, D. M., 1985. Microbes, meiofauna, and bacterial productivity on tubes constructed by the polychaete Capitella capitata.
Marine Ecology Progress Series, 23, 207–208.
Arrieta, N., Goienaga, N., Martínez-Arkarazo, I., Murelaga, X.,
Baceta, J. I., Sarmiento, A., and Madariaga, J. M., 2011.
Beachrock formation in temperate coastlines: examples in
sand-gravel beaches adjacent to the Nerbioi-Ibaizabal Estuary
(Bilbao, Bay of Biscay, North of Spain). Spectrochimica Acta.
Part A, Molecular and Biomolecular Spectroscopy, 80(1),
55–65, doi:10.1016/j.saa.2011.01.031.
Barton, L. L., and Fauque, G. D., 2009. Biochemistry, physiology
and biotechnology of sulfate-reducing bacteria. Advances in
Applied Microbiology, 68, 41–98.
Bates, L., and Jackson, J. A. (eds.), 1987. Glossary of Geology.
Alexandria: American Geological Institute.
Bathurst, R. G. C., 1975. Carbonate Sediments and Their Diagenesis, 2nd edn. Amsterdam: Elsevier.
Behrens, E. W., and Watson, R. L., 1969. Differential sorting of
pelecypod valves in the swash zone. Journal of Sedimentary
Petrology, 39(1), 159–165.
Berner, R. A., 1981. Authigenic mineral formation resulting from
organic matter decomposition in modern sediments. Fortschritte
der Mineralogie, 59, 117–135.
Berner, R. A., and Raiswell, R., 1984. C/S method for
distinguishing freshwater from marine sedimentary rocks. Geology, 12, 365–368.
Bianchi, T. S., 2007. Biogeochemistry of Estuaries. Oxford: Oxford
University Press.
Boer, P. L. D., 1979. Convolutions lamination in modern sands of
the estuary of the Oosterschelde, The Netherlands, formed by
entrapped air. Sedimentology, 26, 283–294.
Boyle, E. A., Edmond, J. M., and Sholkovitz, E. R., 1977. The
mechanism of iron removal in estuaries. Geochimica et
Cosmochimica Acta, 41, 1313–1324.
Brocx, M., and Semeniuk, V., 2009. Coastal geoheritage:
encompassing physical, chemical, and biological processes,
shoreline landforms and other geological features in the coastal
zone. Journal of the Royal Society of Western Australia, 92,
243–260.
Brocx, M., and Semeniuk, V., 2011. The global geoheritage significance of the Kimberley Coast, Western Australia. Journal of the
Royal Society of Western Australia, 94, 57–88.
Brown, A. C., and McLachlan, A., 1990. Ecology of Sandy
Beaches. Amsterdam: Elsevier.
BEACH PROCESSES
71